Device for decolmatation of the critical area of exploitation and injection wells

ABSTRACT

The device for the decolmatation of the critical area of exploitation and injection wells includes a generator of electromagnetic pulses of resonant frequency, which is equipped with a controller (not depicted), and a coaxial cable which connects the generator to a downhole instrument, in which at least two converters for converting electromagnetic energy into mechanical energy are arranged, the converters operating at different frequencies. Furthermore, the converters for converting electromagnetic energy into mechanical energy are arranged in the downhole instrument in series in order of decreasing resonant frequency, and the dimensions of each of the converters are determined by the magnitude of the resonant frequency, each of which differs from the previous one by an integer of octaves. Furthermore, the cable which connects the generator of electromagnetic pulses to the downhole instrument is coaxial with a wave impedance which is equal to the output impedance of the generator and the input impedance of the downhole instrument.

The invention is in the field of oil production, specifically cleaningof the bottom-hole area using ultrasound energy.

To ensure efficacious utilization of wells, it is necessary to removeparaffin and asphaltene deposits on the collectors' pore walls, becausetheir accumulation leads to a decrease in the bottom-hole area'spermeability which in turn causes a decrease in the yield of the welland, on some occasions, completely precludes utilization of the well.

Prior art knows theoretical rationalization of a method of acoustictreatment of the bottom-hole area for the purpose of its decolmatation(O. L. Kuznetsov, E. M. Simkin, G. Chilingar, “Physical foundations ofvibration and acoustic treatment of oil-and-gas reservoirs” M. Mir,2001, pp 106-116); however, said rationalization does not contain adetailed description of a device for decolmatation of the bottom-holearea.

Prior art knows a method and a device for removal of paraffin plugs fromproduced oil using ultrasonic waves (U.S. Pat. No. 7,264,056) comprisingplacement of at least one device generating ultrasonic oscillations nearoil-well tubing, and a device generating variable frequency oscillationsoutside the oil well. The device emits (preferably in a concomitantmanner) ultrasonic oscillations in three fixed frequencies in the rangeof 10 kHz-2000 kHz. Moreover, the first frequency oscillation causesproduction tubing to vibrate and, as a result of that, paraffin plugsare dislodged from the tubing's walls. Second frequency oscillationsdisrupt the connections that hold together paraffin molecules, thussplitting them into smaller particles, and third frequency oscillationssplit long alkanes into shorter molecules.

Prior art knows a method to clean oil-wells and water wells (patent RUNo. 215 1273) that is based on removal of colmatants by periodicallyapplying elastic vibration to the space near the well, comprisingpreparatory evaluation of geological, geophysical, and hydrodynamicinformation about the production well and the data on themajor-parameter dynamics during utilization of the production wells in agiven deposit; determination of the mode of treatment; treatment of theselected production intervals of the bottom-hole area with an elasticvibration field with pre-set parameters; correction of treatmentmodalities based on monitoring the speed of colmatants' removal from thebottom-hole area; and determination of efficacy of the applied treatmentas judged by an increase in the production yield, changes in the fluidmovement profile, and other parameters of the production well,characterized in that during the preparatory evaluation of themajor-parameter dynamics while using the well in a given deposit,productivity, water-cut, oil-gas ratio, bottom-hole pressure, anddeposit pressure are measured and analyzed during the well's use; basedon said analyses, wells are selected for which a decrease in the yieldis due to colmatation of the bottom-hole area in the production depositswith preservation of high deposit pressure; and for each deposit inthese wells, the following parameters are determined: the mode oftreatment comprising treatment intervals, the pace of treatment, thefrequency and the intensiveness of elastic vibrations, and the order ofcontinuous or pulse-type treatment over various intervals; moreover,using the curves reflecting a decrease in the yield, the sequence of thetreatments is determined for various wells with a consideration of theextent to which the yield is decreased, and the data obtained in thecourse of assessing the efficacy of the performed treatment is used toadjust the mode of the well's utilization.

Prior art knows a method of acoustical treatment of a bottom-hole areaof a production deposit (patent RU No. 2026969) comprising applying anacoustic field onto the zone near the well, characterized in that, inorder to increase productivity of the deposit by means of restoringfiltration properties of its bottom-hole area, the filtration propertiesof the bottom-hole area are measured prior to the deposit's treatment;areas with low filtration properties are identified; and the deposit'streatment is carried out in a consistent, point-by-point manner in theup-down direction by multiple rounds of subjecting the bottom-hole areasites with low filtration properties to an acoustic field whoseintensity is at least 0.2 W/cm²; moreover, following each treatmentround, filtration properties are measured, the dynamics of theirrestoration are determined and, based on the results of saiddeterminations, intensity and duration of the acoustic treatment areincreased until the filtration properties are stabilized.

Prior art knows a method (patent RU No. 2296215) of treating thebottom-hole well area—employed in the capacity of a prototype—comprisinglowering into the well's perforation interval, on a column of oil-welltubing, a setup consisting of a packer, a paired sucker-rod pump with abody comprising an upper and a lower body connected by a perforatedduct, a column of spears with a plunger, and an ultrasound generator;separating inter-tubing space above the perforation interval by thepacker; applying ultrasonic-frequency elastic vibrations to thebottom-hole area of the well in the medium of active technological fluidand acid solution; suctioning off reaction products with simultaneouswashout of treatment products; treating the deposit with ultrasound; andcreating alternating motion of the fluid in the perforation interval andweak depression pulses, characterized in that a mechanical ultrasoundgenerator is used as an ultrasound generator that works when a stream ofliquid passes through it in one direction while the ultrasonic treatmentis carried out when the liquid is supplied into oil-well tubing by thepump during the fourth part of the pump's cycle.

The known methods and devices feature low efficacy of decolmatation ofthe bottom-hole area of production wells, and their manufacture andutilization are complex.

The goal to be achieved with the invention being claimed is to create adevice that is able to increase the efficacy of treatment of thebottom-hole area using the minimally possible dimensions of thedown-hole apparatus.

The invention being claimed achieves said goal by placement, in thedown-hole instrument, of no less than two converters of electromagneticenergy into mechanical energy that work at different frequencies.Moreover, the converters of electromagnetic energy into mechanicalenergy are positioned in a down-hole instrument sequentially in theorder of decreasing resonant frequency, while the size of each converteris defined by the resonant frequency magnitude, and each subsequentfrequency differs from the previous one by the whole integer of octaves.Further, the cable connecting the generator of electromagnetic pulsesand the down-hole instrument is coaxial with wave impedance equal to theoutput impedance of the generator and the input impedance of thedown-hole instrument.

A suggested schematic of the invention “A device for decolmatation ofthe bottom-hole area of production and injection wells” is shown in FIG.1, where 1—ultrasound converters of electromagnetic energy intomechanical energy; 2—bottom-hole area; 3—perforation zone; 4—down-holeinstrument; 5—oil-well tubing; 6—casing pipe; 7—well; 8—coaxial cable;9—winch; 10—generator of resonant frequency electromagnetic pulses witha controller (not shown for clarity); 11—geophysical lifter.

The device operates as follows (see FIG. 1).

A signal of the corresponding frequency from generator 10 equipped witha controller (not shown for clarity) passes via coaxial cable 8 toconverters of electromagnetic energy into mechanical energy 1. Usingultrasound with a higher frequency ensures maximally intensive treatmentunder conditions with small radii, whereas ultrasound with a lowerfrequency allows for coverage of a broader volume of the bottom-holezone. Moreover, the generator's controller (not shown for clarity) formsa signal of the required shape, which is harmonic with stepwiseenveloping. In this case, each of converters 1 is tuned to the specificharmony of the overall signal. Converters of electromagnetic energy intomechanical energy 1 are positioned in down-hole instrument 4sequentially in the order of decreasing resonant frequency, while thesize of each converter is defined by the resonant frequency magnitude.Each subsequent frequency differs from the previous one by the wholeinteger of octaves. Coaxial cable 8 features wave impedance equal to theoutput impedance of generator 10 and the input impedance of down-holeinstrument 4, thus ensuring that the target shape of the signal ismaintained.

It has been demonstrated experimentally that multi-frequency treatmentafforded by the invention being claimed, significantly increases theyield of wells when compared to mono-frequency treatment (see Table 1).

TABLE 1 Average increase in the yield following multi-frequency andmono-frequency ultrasonic treatment of the well's bottom- hole areaAverage Average Average yield, yield, yield, 1-10 tons/ 10-30 tons/ >30tons/24 24 hours 24 hours hours Terrigenous deposits Mono-frequency50-70% 10-25% 5-10% treatment (frequency: 25 kHz) Multi-frequency70-110% 25-45% 8-15% treatment Carbonate deposits Mono-frequency 30-50%15-25% 3-8% treatment (frequency: 25 kHz) Multi-frequency 40-70% 35-50%5-10% treatment

Thus, the invention being claimed allows one to significantly increasethe depth of the efficacious treatment of the bottom-hole area with theminimally possible dimensions of the down-hole instrument.

1. A device for decolmatation of the bottom-hole area of production andinjection wells, comprising a generator of electromagnetic pulses ofresonant frequency and a coaxial cable connecting the generator to adown-hole instrument, wherein, in order to increase the depth of theefficacious treatment of the bottom-hole area, the down-hole instrumentcontains no less than two converters of electromagnetic energy intomechanical energy; moreover, the signal sent from the down-holeinstrument's generators to the converter of electromagnetic energy intomechanical energy is harmonic with stepwise enveloping, and each of theconverters is tuned to the specific harmony of the overall signal. 2.The device of claim 1, wherein the converters of electromagnetic energyinto magnetic energy are positioned in the down-hole instrumentsequentially in the order of decreasing resonant frequency, while thesize of each converter is defined by the resonant frequency magnitude,and each subsequent frequency differs from the previous one by a wholeinteger of octaves.
 3. The device of claim 1, wherein the generator ofelectromagnetic pulses is equipped with a controller that enables one toform a signal with the required shape.
 4. The device of claim 1, whereinthe cable is coaxial with wave impedance equal to the output impedanceof the generator and the input impedance of the down-hole instrument.